中原大學九十二學年度博士班入學招生考試

92年6月11日 08:30~10:00 應用數學系   誠實是我們珍視的美德,
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科目:機 率 (共1頁第1頁)

1 For a random variable X, show that the set function is a probability on R. (10%)
   
2 Let s be chosen according to the uniform distribution from (0, 1). Now let Xn be defined as for n=1,2,... Why does the monotone convergence theorem fail here? (15%)
   
3 Let and F(x) be the characteristic function and distribution function of a random variable X, respectively. For any two real numbers a and b, a<b, which are continuity points of F(x), show that
(20%)
   
4 Suppose that the number of customers, N(t), arrive at a service station at time t, , in accordance with a Poisson process having rate . Upon arrival, a customer is immediately served by one of an infinite number of possible servers, and the service times are independent random variables having a common distribution function G.
  a) Given that N(t)=n, find the joint distribution of the n arrival times S1,...,Sn. (10%)
  b) What is the distribution of X(t), the number of customers that have completed service by time t? (10%)
   
5 Let and Xi and Yi, i=1,.., K, be independent binomial variables with X i~and Yi~. In the case of , find the large-sample distribution of the random variable , where , as the sample size n approaches infinity. (15%)
   
6 Consider a machine that works for an exponential amount of time having mean before breaking down; and suppose that it takes an exponential amount of time having mean to repair the machine. If the machine is in working condition at time 0, then what is the probability that it will be working at time t=10. (20%)
   
 
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